46 Mr. JVehster's Reply to Dr. Fit ton. [Jan. 



mined the isle of Purbeck, and presented to the Geological 

 Society a complete set of specimens of all the beds), I could 

 not conceive what had led to this mistake, and turned over 

 my letters to Sir H. Englefield in search of any passage that 

 could bear such a construction. The only one that appears to 

 be the least obscure is that where I mention (p. 122) the thin 

 layers with shells in a clay (the weald clay), in Sandown Bay, 

 called Flatten, respecting which 1 observe, that " they miicli 

 resemble Purbeck stone, but the shells are larger." It must be 

 obvious, that by this 1 mean only that the two kinds of stone 

 have much the same appearance, without any attempt to identify 

 the beds from which they came. I had not at that time seen 

 the Purbeck stone in situ, and spoke merely of it as knowing it 

 in building. Indeed that no other inference can be fairly drawn 

 from my expression is evident, since Dr. Fitton himself says, 

 p. 374, that " the limestone of the weald bears altogether a strik- 

 ing resemblance to the Purbeck hmestone ;" and yet he does 

 not intend to express they are the same. My having mentioned 

 this resemblance shows that at a very early period of my inves- 

 tigation, I was struck with an analogy between the Platten 

 in the Isle of Wight, and the Purbeck and Petworth marbles, an 

 analogy which 1 have since extended. 



Dr. Fitton is perfectly correct in stating, that, at the time when 

 I wrote those letters to Sir H. Englefield, I had not duly appre- 

 ciated the importance of the weald clay. The fact is, it is far 

 less conspicuous in the Isle of Wight as a valley separating two 

 ranges of high ground than in Kent and Sussex ; nor, at that early 

 period, had the difference between the fossils of the Hastings 

 beds and the Folkestone rock been noticed. But I had been 

 gradually approaching, and had finally arrived at the same con- 

 clusion as Dr. Fitton has now done. 



I mentioned in my paper on the Freshwater Formations of 

 the Isle of Wight, and also in one of my letters to Sir H. Engle- 

 field,* the probability, that part, at least, of the Purbeck series 

 Avas of freshwater origin ; and I possess specimens which I 

 brought with me from the Purbeck beds on my first visit to 

 them in 1812, containing several species of freshwater shells 

 converted into caicedony, but mixed with others that are marine. 

 I also stated in my table of the strata, that the Petworth marble 

 might perhaps belong to the same series, from the analogy in its 

 fossils. The univalve shells of the Petworth marble are in gene- 

 ral larger than those of the Purbeck, but I have since found beds 



* The passage is as follows: — " It was long ago observed by AVoodwaril, in his 

 History of Fossils, that the shells in the Purbeck marble consisted chiefly of the helix 

 vivipara; and it is rather surprising that this very ancient freshwater formation should 

 not have excited more attention. Beautiful impressions offish are frequently met with 

 by the quarrymen between the laminae of the limestone; and ] saw abundance of frag- 

 ments of bones, some of which belonged to the turtle. Complete fossil turtle have been 

 found, and lately one extremely perfect," (Letter 9, p. 192.) 



